<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2015, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package    CodeIgniter
 * @author    EllisLab Dev Team
 * @copyright    Copyright (c) 2008 - 2014, EllisLab, Inc. (http://ellislab.com/)
 * @copyright    Copyright (c) 2014 - 2015, British Columbia Institute of Technology (http://bcit.ca/)
 * @license    http://opensource.org/licenses/MIT    MIT License
 * @link    http://codeigniter.com
 * @since    Version 3.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * PHP ext/hash compatibility package
 *
 * @package        CodeIgniter
 * @subpackage    CodeIgniter
 * @category    Compatibility
 * @author        Andrey Andreev
 * @link        http://codeigniter.com/user_guide/
 * @link        http://php.net/hash
 */

// ------------------------------------------------------------------------

if (is_php('5.6'))
{
    return;
}

// ------------------------------------------------------------------------

if ( ! function_exists('hash_equals'))
{
    /**
     * hash_equals()
     *
     * @link    http://php.net/hash_equals
     * @param    string    $known_string
     * @param    string    $user_string
     * @return    bool
     */
    function hash_equals($known_string, $user_string)
    {
        if ( ! is_string($known_string))
        {
            trigger_error('hash_equals(): Expected known_string to be a string, '.strtolower(gettype($known_string)).' given', E_USER_WARNING);
            return FALSE;
        }
        elseif ( ! is_string($user_string))
        {
            trigger_error('hash_equals(): Expected user_string to be a string, '.strtolower(gettype($user_string)).' given', E_USER_WARNING);
            return FALSE;
        }
        elseif (($length = strlen($known_string)) !== strlen($user_string))
        {
            return FALSE;
        }

        $diff = 0;
        for ($i = 0; $i < $length; $i++)
        {
            $diff |= ord($known_string[$i]) ^ ord($user_string[$i]);
        }

        return ($diff === 0);
    }
}

// ------------------------------------------------------------------------

if (is_php('5.5'))
{
    return;
}

// ------------------------------------------------------------------------

if ( ! function_exists('hash_pbkdf2'))
{
    /**
     * hash_pbkdf2()
     *
     * @link    http://php.net/hash_pbkdf2
     * @param    string    $algo
     * @param    string    $password
     * @param    string    $salt
     * @param    int    $iterations
     * @param    int    $length
     * @param    bool    $raw_output
     * @return    string
     */
    function hash_pbkdf2($algo, $password, $salt, $iterations, $length = 0, $raw_output = FALSE)
    {
        if ( ! in_array($algo, hash_algos(), TRUE))
        {
            trigger_error('hash_pbkdf2(): Unknown hashing algorithm: '.$algo, E_USER_WARNING);
            return FALSE;
        }

        if (($type = gettype($iterations)) !== 'integer')
        {
            if ($type === 'object' && method_exists($iterations, '__toString'))
            {
                $iterations = (string) $iterations;
            }

            if (is_string($iterations) && is_numeric($iterations))
            {
                $iterations = (int) $iterations;
            }
            else
            {
                trigger_error('hash_pbkdf2() expects parameter 4 to be long, '.$type.' given', E_USER_WARNING);
                return NULL;
            }
        }

        if ($iterations < 1)
        {
            trigger_error('hash_pbkdf2(): Iterations must be a positive integer: '.$iterations, E_USER_WARNING);
            return FALSE;
        }

        if (($type = gettype($length)) !== 'integer')
        {
            if ($type === 'object' && method_exists($length, '__toString'))
            {
                $length = (string) $length;
            }

            if (is_string($length) && is_numeric($length))
            {
                $length = (int) $length;
            }
            else
            {
                trigger_error('hash_pbkdf2() expects parameter 5 to be long, '.$type.' given', E_USER_WARNING);
                return NULL;
            }
        }

        if ($length < 0)
        {
            trigger_error('hash_pbkdf2(): Length must be greater than or equal to 0: '.$length, E_USER_WARNING);
            return FALSE;
        }

        $hash_length = strlen(hash($algo, NULL, TRUE));
        if (empty($length))
        {
            $length = $hash_length;
        }

        $hash = '';
        // Note: Blocks are NOT 0-indexed
        for ($bc = ceil($length / $hash_length), $bi = 1; $bi <= $bc; $bi++)
        {
            $key = $derived_key = hash_hmac($algo, $salt.pack('N', $bi), $password, TRUE);
            for ($i = 1; $i < $iterations; $i++)
            {
                $derived_key ^= $key = hash_hmac($algo, $key, $password, TRUE);
            }

            $hash .= $derived_key;
        }

        // This is not RFC-compatible, but we're aiming for natural PHP compatibility
        return substr($raw_output ? $hash : bin2hex($hash), 0, $length);
    }
}
